With half of U.S. pregnancies each year being unintended there is a great need to seek novel approaches to address this persistent public health issue. Efforts that expand access to highly effective methods of contraception to women at high risk of unintended pregnancy have demonstrated reductions in unintended pregnancies and abortions. Women presenting for emergency contraception (EC) comprise an ideal population in which to initiate highly effective reversible contraception, as they are at a high rik of unintended pregnancy and are acting to reduce that risk. The copper IUD possesses two advantages over the common oral hormonal methods of EC: it is the most effective method of EC and it continues to provide highly effective contraception for up to 12 years. Our recent publication demonstrated a significantly lower pregnancy rate 12 months after presenting for EC among women who selected the copper IUD versus those who selected oral levonorgestrel (LNG). However, women selecting intrauterine contraception have shown a strong preference for the levonorgestrel (LNG) IUD because it reduces or eliminates menstrual bleeding and discomfort. As the LNG20 IUDs effectiveness for EC remains unknown our multi-disciplinary Family Planning Research Group proposes a randomized controlled trial to assess the safety and efficacy of the LNG IUD as EC. The main goal of this research is to evaluate the innovative use of the LNG20 IUD alone for EC in a population of predominantly low-income women. Utilizing the same clinical sites we have consistently employed to study the IUD for EC since 2008 we will randomly assign 706 women presenting for EC to either the LNG20 IUD or the copper T380 IUD. Our primary aim is to assess the efficacy of the LNG20 IUD vs. the copper T380 IUD for EC utilizing a non- inferiority design. We will also assess one-year continuation and unintended pregnancy rates in women initiating the LNG20 IUD or copper T380 IUD for EC and study the mechanisms of continuation related to satisfaction, pain, and bleeding over the first year of use. This proposal builds on the strong foundation laid by our successful R21 assessing the copper IUD for EC and serves as the next innovation in our growing research program offering highly effective reversible contraception at the time women present for EC. Demonstrating the efficacy, safety, and acceptability of the LNG20 IUD for EC will improve options for women seeking EC and has the potential to eliminate a significant barrier to IUD initiation, increase IUD use, and lower the persistently high rate of unintended pregnancy in the U.S. 1